Transient signal recordingreproducing device



June 19, 1945. J. P. ARNDT, JR

TRANSIENT SIGNAL RECORDING-REPRODUCING DEVICE Filed Oct. 17, 1942 2 Sheets-Sheet 1 FILTER FILTER 'J' DET. I

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IN V EN TOR. JOHN P ARNDT JR. BY

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June 1945- J. P. ARNDT, JR 2,378,383

TRANSIENT SIGNAL RECORDING-REPRODUCING DEVICE Filed Oct. 17, 1942 2 Sheets-Sheet 2' FILTER FIEA AMP

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Patented June 19, 1945 TRANSIENT SIGNAL RECORDING- REPRODUCING DEVICE John P. Arndt, Jr., Euclid, Ohio, assignor to The Brush Development Company, Cleveland, Ohio,

a corporation of Ohio Application October 17, 1942, Serial No. 462,395

15 Claims.

This invention relates to transient analyzer systems, and more particularly to transient analyzer systems of the type described and claimed in the copending application Serial No. 425,304, filed January 1, 1942, by S. J. Begun. In such transient analyzer systems, transient phenomena that may occur on an electric circuit are studied by continuously making an obliterable record of the circuit conditions under study on an endlessly-oper ating cyclically-effective recording medium, such as a magnetic recording medium, so that the circuit conditions are continuously recorded; the continuous recording operation being'accompanied by a continuous obliteration of the recordings and. the obliterating action being stopped upon the occurrence of a transient condition so as to retain on the recording medium a record of a si nal corresponding to the transient occurrence and the recording operation being discontinued after the transient occurrence has been 'recorded on the medium in such manner as to enable the study of the transient occurrence by cyclically reproducing the record and utilizing the reproduced record for operating a cyclically-operative indicating device, such as an oscilloscope, which presents an image corresponding to the reproduced signal upon each cycle of the recordin medium.

.Among the objects of the invention is a transient analyzer of the foregoing type which makes it possible to study simultaneously two or more transient occurrences which may happen substantially simultaneously.

The foregoing and other objects of the invention will be best understood from the following description of exemplificat ons thereof, reference be- 1r 2 had to the accompanying drawings wherein- Figure 1 is a block diagram of my multi-cha-nnel transient recording and/or reproducing device.

Figure 2 is a block diagram of a multi-channel device somewhat similar to the device shown in Figure 1 but utilizing three recording and reproducing means, and in which one of the channels is used for determin ng the duration of a transient. I

Figure 3 shows the picture available on the screen of an oscilloscope utilizing the apparatus of Figure 2.

Figure 4 illustrates a form of my invention in which three transient'signals may be recorded and reproduced.

In Figure 1 there are two si nal input channels A and B to a single amplifier 28. The channel A comprises an oscillator I0, a modulator l2. and a channel B comprises an oscillator II, a modulator I3, and a filter l5 connected to the same amplifier 20. The input terminals l6, l8 to chane1 A may be connected to an outside circuit such as a power line in such a manner that any voltage transient inthe power line will establish a signal in the channel A, and the input terminals l1, l9 to channel B may be connected to the same outside power line in such a manner that any current transient in the power line will establish a signal in the channel B.

' This device is being described using as examples current and voltage transients. It is to be understood, however, that other transients can be studied and that my device is not limited to two transients.

The oscillator I is tuned to a certain frequency, say 2 kc. and is'connected to the modulator I2. When the voltage signal transient is applied to the input terminals l6, I8 of the modulator ill, the 2 kc. carrier signal from the oscillator I0 is modulated in accordance with the voltage transient signal. The filter I4 is designed to pass to the amplifier 20 a signal having a frequency range which includes the high and low side bands of the signal modulated carrier. For instance, if the transient is not expected to have components exceeding 500 cycles per second, then the filter can have a pass range from ,1500 to 2500 cycles per second. From the filter M the signal modulated carrier passes to the amplifier 20.

The oscillator II is tuned to a frequency which differs from the frequency of the oscillator l 0, say 4 kc., and is connected to the modulator I3. When the current signal transient occurs, the 4 kc. carrier signal from the oscillator ii is modulated in accordance with the current transient signal. The filter I is designed to pass to the amplifier 20 a signal having a frequency range which includes the high and low sid bands of the signal modulated carrier. In this case the pass range of the filter will be from 3500 to 4500 cycles per second. From the filter [5, the current signal modulated carrier passes to the amplifier where it is superposed on the voltage signal modulated carrier to establish what may be called a composite signal. The amplifier 20 should be able to amplify and pass signals having a range from 1500 to 4500 cycles per second or greater and should be very free from modulating effects.

The output current from the amplifier 20 is fed to a magnetic recording head 24 which is p0- sitioned in magnetic flux linkage relationship to an endless magnetic tape 25. The tape is confilter it connected to the amplifier 20; and the tinuously driven about rollers 26, 21 by a motor ismmnm. l. H

2a, and the lengthrof the tape is suflicient that the entire transient can recorded on it during one revolution.

Switching means, such as are described in detail in the Begun application, may be provided for stopping the recording and obliterating functions at the proper times so that the recorded transient will not be distorted or lost. If the circuit to which the apparatus is connected nor- .mally carries steady state alternating current,

29 is applied to the input of amplifier 30, and the output is fed to each of two filters 3|, 32. Filter 3| has a pass band corresponding to the pass band of filter I5, and so passes to the detector 33 only the current signal modulated carrier, and filter 32 has a pass band corresponding to the-pass band of filter l4, and so passes to the detector 34 only the voltage signal modulated carrier. The detectors 33, 34 may include suitable filters for removing the carrier and its side band components. From the detectors 33 and 34 there are derived two signals which are substantially facsimiles of the two transients which were fed into the modulators l3 and I2. These two signals are established for each revolution of the magnetic tape past the reproducing head 29, and are used to control a cathode ray oscilloscope 35. A switch 36 which may be mechanical but which preferably is electronic, is provided between the outputs from the detectors 33, 34 and the oscilloscope 35 for alternately connecting first one detector and then the other detector to the oscilloscope. In this manner, and by synchronizing the action of the switch and the horizontal sweep circuit of the cathode ray oscilloscope with the rate of rotation of the magnetic tape 25 upon which the signals were recorded substantially simultaneously, the cathode ray will successively trace on its screen an image corresponding to one transient signal followed by an image corresponding to the other transient signal. Due partly to the persistence of the screen and partly to the persistence of vision the observer will see on the screen both images in their proper time phase relationship.

In the copending application Serial No. 425,304, filed January 1, 1942, by S. J. Begun and assigned to the assignee of the present application, there is described in connection with Fig. 5 an electronic switch arrangement which will perform the functions of the switch 36 described above, and reference is made to said application for a description thereof.

The oscilloscope 35 may be of the type described, for instance, in Shepard Patent 2,221,115, issued November 12, 1940, and its horizontal time axis sweep may be synchronized with the investigated signals or by a separate pulse generated by an element associated with the motion of the tape, such as a tape joint or tape protrusion. As is well known, such cathode ray oscilloscopes are equipped with synchronizing switch means,

cea e such as the switches'sl, Side scribed 'in-oonnec- "tlon wlth l 'igez-of the Shepard Patent 2,221,115,

which has a position in which the time axis sweep is automatically synchronized by the investigated signals, and such oscilloscope arrangement is suitable for a system of the invention.

The two diiferent traces on the oscilloscope will occupy substantially the same portion of the screen. For some transients and uses these two overlapping traces will not interfere with each other and determination of accurate phase relation is made easy. However, if the operator desires to separate the two traces biasing means such as batteries 31. and 38 may be provided. The battery 31 is polarized to bias the beam from the detector 33 upwardly from the center of the screen, and the battery 38 is polarized to bias the beam from the detector 34 downwardly from the center of the screen thereby separating the two signal images as shown on the screen 39 of the oscilloscope 35. Such biasing effects are usually provided for in commercially available electronic switches.

It will be seen from this description that each trace e and each trace z" on the screen 39 appears only once for each two revolutions of the magnetic material 25. However, in case the persistence of the screen 39 is not sumcient to provide substantially sustained pictures of the two transients the rate of rotation of the magnetic material during reproduction may be increased. Other channels may be provided if more than two phenomena are to beobserved. An obliterating head 23 connected through switch 85 to a source 84 of obliterating current is provided. When the switch 85 is closed the record on the tape 25 will i be obliterated to prepare the tape for a subsequent record.

For many of the uses of the transient recording and reproducing device it may be convenient or necessary to determine with a fair degree of accuracy the duration of the transient. For this purpose one channel of the multi-channel system may carry a timing wave.

Figure 2 illustrates an alternative way of providing multi-channel recording, and as illustrated includes a plurality of transient channels one of which includes a means for causing a trace of a known alternating frequency to appear on the screen of the oscilloscope as a timing wave, together with the traces of the transient signals as is shown in Figure 3. The timing signal may appear as a series of sinusoidal cycles, and knowing the frequency of the timing signal, a fairly good indication of the duration of the transient signal can be obtained by comparing the length of the transient signal with the timing signal. An advantage of the device of Figure 2 over the device of Figure 1 is that it has a better dynamic range.

My device comprises a plurality of endless magnetic record members 50, 5| and 52 driven at a constant rate of speed by a motor 28. Associated with the member 50 is a recording head 53, an obliterating head 56, and a reproducing head 59.

Associated with the member 5| is a recording] head 54, an obliterating head 51, and a reproducing head 60. Associated with the member 52 is a recording head 55, an obliterating head 58 and a reproducing head 6|. Although I have shown three separate recording-reproducing systems, it is to be understood that a single record member such as a disk of magnetic material could be used, and recording-reproducing and obliterating head positioned with respectto the disk so that a plurality of record tracks are utilized. This system would automatically eliminate any trouble arising from one track moving at reate ate of speed than the other track.

A first tran ent signal corresponding, for instance. to the v tage transient, is applied to input terminals I6, I 8 of the amplifier 65 the output of which is connected to the recording head 53. The recording head magnetizes the magnetic member 50 in accordance with the transient signal according to any of the known methods. The carrier method described in connection with Figure 1 can also be used by providing an oscillator and a modulator in the input circuit and suitable filters and detectors in the output circuit. The reproducing head. 59 establishes a signal which is substantially a facsimile of the recorded signal. The signal is amplified by the amplifier G6 and the output is obtainable between the oscilloscope 83, and the segment 68 of switch 69. An oscillgtor ID of known-frequency is connected to the recording head 54 whichmagnetically records an alternating signal on the magnetic material 5I. This signal is reproduced by the head 68, amplified by the amplifier II, and the output is obtainable between the oscilloscope 83 and the seg ment 13 of the switch 68.

A second transient signal corresponding. for instance, to the current transient, is applied to input terminals I1, I!) of the amplifier I6 the output of which is connected to the recording head 55 and magnetizes the magnetic member 52 in accordance with the transient signal. The reproducing head 6| is associated with the magnetic member 52 and establishes a signal which is substantially a facsimile of the recorded signal. The reproduced signalis amplified at I1 and the output is obtainable between the oscilloscope 83 and the segment I9 of the switch 69. Associated with the three segments 68, I3, I9 is a switch arm 88 which is rotated in synchronism with the rotation of the recording mediums 58, 5I, 52. A 3:1 speed reduction device 82 is provided between the motor 28 and the arm 88. This synchronism and the speed reduction cause the arm 80 to sweep one segment of the switch 69 for each rotation of the recording medium. One side of each amplifier 66, I I, I1 is connected to one plate of the cathbde ray oscilloscope 83, and another plate is connected to the arm 80. As the arm 88 sweeps across one segment of the switch 69. say for instance the segment 68, the output of the amplifier 66 is connected to the cathode ray oscilloscope for one complete revolution of the recording medium. The arm 88 has then moved to the next segment 13 and the oscilloscope 83 is connected to the output of the amplifier II for the next complete revolution of the recording medium. The arm 88 has then moved to the next segment I9 and the oscilloscop 83 is connected to the output of the amplifier 11 for the next complete revolution of the recording medium. Rapid repeated rotation of the recording medium and switch arm 80 will result in three signals being visible on the screen of the cathode ray oscilloscope 83. One will be the timin wave,

one will e the voltage transient signal, and the other will be the current transient signal. The sweep circuit of the oscilloscope should be synchronized with the rate of rotation of the tape so that there i one sweep of the oscilloscope for each rotation of the recording medium.

The position Of switch arm 80 on the contact segments in relation to the positions of the recorded transients on the magnetic members may be made adjustable, for example, by making the switch segment holder .manually rotatable, so that the transient pictures may be suitably "phased on the cathode ray oscilloscope screen.

The motor 28 should drive the medium fast enough that due to the persistence of the oscilloscope screen and the persistence of vision practically a sustained trace of both the transient signals and the timing signal will be seen. Thus the physical length of the trace of the transient sig als can be compared to each other and to the length of the timing signal which is of a known frequency, and the duration of the transients determined. Batteries 31 and 38 may be provided for causing the two transient traces to appear on different portions of the oscilloscope screen. A source 84 of obliterating current is connected to the obliterating heads 56, 51, 58 when the switch 85 is closed, for erasing or obliterating the magnetic record on the magnetic material and so prepare it for a subsequent record. Automatic switching of the recordingreproducing and obliterating signals upon occurrence of the transient may be incorporated as described in the Begun application. Obviously, the signal to the head 54 can also be a transient signal. I prefer to record the timing wave directly on to the magnetic record material and then to play it back into the oscilloscope rather than apply it directly to the oscilloscope because it is simpler to obtain relative immobility between the transient signal and the timing signal. If the timing signal were applied directly to the oscilloscope, and if the signal were not a harmonic of the frequency at which the magnetic material was being driven, the trace of the timing signal on the oscilloscope would move with respect to the traces of the transient signals. By recording the timing wave on the record material it becomes fixed with respect to the recorded transient signals, and upon reproduction into an oscilloscope that fixed relationship will be retained.

Figure 4 illustrates another form of my invention in which three transient signals may be recorded and reproduced to enable a person to analyze each transient and to determine the phase relation between them. In this system no switch such a 36 in Figure 1 or 69 in Figure 2 is necessary. A magnetic material such as the endless tape IIlIl is driven around rollers in the direction of the arrow at a constant rate of speed by motor II. The length of the tape and the rate of rotation are chosen so that the entire transient signal which is to be recorded thereon will not occupy more than one-third of the tape. In a two transient system the length and speed of the tape are such that the transient will occupy one-half or less of the tape. and in a four transient system the length and speed of the tape are such that the transient will occupy onefourth or less of the tape. The length of the tape is so chosen in order that no two reproducing heads will simultaneously reproduce the recorded signal. One recording head I02 and one obliterating head I03 are provided and are.

spaced about the path of thetape so that the distance from the recording head I02 to the obliterating head I03 in the direction of movement of the tape is one-third of the entire length l of the tape. Three reproducing heads I04, I05.

I86 are provided and are spaced about the path of the tape I08 so that one-third of the length of the tape separates each head from each of the other two heads.

The recording head I02 is fed a signal comprised of three carrier currents f1, f2, f3, established by the oscillators I01, I08, I09 and each is modulated by a different transient signal. The first transient signal is app at nput terminals IIO of the modulator H3 and the output of the modulator is connected to the amplifier H6. The second transient signal is applied at input terminals III of the modulator H4 and the output of the modulator is connected to the amplifier H6. The third transient signal is applied at input terminals II2 of the modulator II5 and the output of the modulator is connected to the same amplifier II6. Either amplitude or frequency modulation may be used. The frequencies f1, f2, and is of the three oscillators I01, I08 and I09 are sufficiently difierent from each other that their upper and lower side bands after modulation by the three transient signals do not overlap and they are all combined into a composite signal which is impressed on the amplifier H6. This composite signal is amplified by the amplifier H6 and fed to the recording head I02 which records the composite signal on the moving tape I00. The composite signal so recorded on the moving tape I00 is reproduced, first by the pickup head I06, then after a slightly longer time delay by the pickup head I05, and finally after a little more time delay by the pickup head I04. The signal outputs from heads I04, I05, I06 are amplified by amplifiers I25, I26 and I24 respectively and the amplified signal outputs are passed to filters I28, I29 and I21 respectively. The filter I28 is tuned to pass frequencies in the range of f1, including its sidebands and to reject all other frequencies. Filter I21 is tuned to pass frequencies in the range of f3, including its sidebands and to reject all other frequencies. Filter I29 is tuned to pass frequencies in the range of f2, including its side bands and to reject all other frequencies. The signal outputs from filters I21, I28, I29 are fed to detectors I30, I3I, I32 respectively, and then fed to the cathode ray oscilloscope I33. A synchronizing connection I34 to the sweep circuit I 35 of the oscilloscope I 33 is made to cause the beam to make three sweeps for each revolution of the tape I00. Due to this synchronization, and to the fact that the three reproducing heads are spaced at the one-third points on the path of the tape, and to the fact that each head and its associated circuit equipment passes only one transient signal, there will be presented on the screen of the oscilloscope three separate and independent pictures during each revolution of the tape I00. Each of these pictures will. be substantially a facsimile of one of the transient signals which was applied at the input terminals IIO, III, II2.

Associated with the recording head I02 and with the obliterating head I03 is a trigger circuit I43. The trigger circuit is connected to the transient signal input terminals H0 and actuates a relay I44 to open switches I45 and I46. The switch I45 is in the line between the oblitcrating head I03 and the obliterating current source I41, and the switch I46 is in the line between the recording amplifier I I6 and the recording head I02. The trigger circuit is set in operation by the occurrence of a transient and operates the relay I44 only after a, time delay corresponding in duration to the length of time necessary for the tape I00 to complete one-third of a revolution. By this time the entire transient, including the very first portion, is recorded on the tape I00, and the transient is retained on the tape due to the opening of switch I45 which controls the supply of obliterating current to obl1terating head I03. After the entire transient has been recorded on the tape I00, the switch I46 is opened by relay I44 to prevent the recording of signals corresponding to f1, f2, f; on the portion of the tape on-which the transient signal was recorded. For a more detailed description of the transient operatedgrtrigger circuit including the re-energization of relay I44 reference may be made to the Begun "application Serial No. 425,304, filed January 1, 1942. 3

After the relay I44 has thrown open the switches I45 and I46 in the obliterating and recording circuits, the tape I00 will have recorded on one-third or less of its length, a composite signal made up of the three signal modulated carriers. The remaining two-thirds of the tape will have no signal since that portion of the tape will have been obliterated by the head I03 prior to the opening of switch I45, and the opening of switch I46 will haveprevented a signal from being recorded on the obliterated two-thirds of the tape. I utilize the one-third of the tape on which a signal has been recorded to provide a biasing action of the cathode ray oscilloscope beam.

When the unrecorded portion of the tape is passing a reproducing head there is no signal to reach the rectifier associated with that head and hence there is no rectifier output. However, when the recorded portion of the tape passes a reproducing head, the rectifier associated with that head has an output consisting of a direct current component whose strength corresponds to the amplitude of the carrier to which that channel is tuned, with a transient signal superimposed on the direct current voltage. This direct current component, available at any time only from the channel that is reproducing its transient at that time, is used to bias the cathode ray oscilloscope beam to a suitable position. The outputs of the 3 rectifiers I30, I3I, and I32 are connected in series with the polarities of I3I and I32 in aiding relationship to each other and in opposing relationship to I30. Thus the direct current components of I3I and I32, each in their turn, bias the oscilloscope beam in one direction, while the direct current component of I30, when it occurs, biases the beam in the opposite direction. Potentiometers I40, I4I, I42 are provided so that any desired portion of each direct current component may be selected. These potentiometers, therefore, act as vertical position trace controls. To prevent the potentiometers from influencing also the amplitudes of the individual transient traces, a separate transient signal path is provided through condensers I50, I5l, I52, and resistors I53, I54, I55 are inserted to prevent these condensers from shunting portions of the potentiometers.

Throughout the description of my methods and devices I speak of modulating the carrier current by the transient signal which is to be studied. It is to be understood thatthis modulation can be either amplitude or frequency modulation or any other suitable form of modulation or combination of diiferent kinds of modulation without departing from the spirit of my invention.

Although I have described my invention with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of. example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

I claim as my invention: l

1. In a system for studying transient signal occurrences and associated witha source of at least a first transient signal and second transient signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable frequenc range; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal; recording means for recording on said medium signals corresponding to said first signal and second signal; reproducing means including demodulating means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first signal and a second reproduced signal corresponding to said second signal; and cyclically-operative indicating means cyclically actuated by said different reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from the cyclically moving medium.

2. In a system for studying transient signal occurrences and associated with a source of at least a first transient signal and second transient signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable fre- I quency range; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal; recording means for recording on said medium a composite signal corresponding to said first modulated signal and second modulated signal; reproducing means including demodulating means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal correof saidvcarrier currents being .of a frequency reproducibly recordableon said moving recording medium; modulating means for modulating the.

firstcarrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal; recording means for recording on said medium signals corresponding to said first signal and second signal; reproducing means including demodulating means for cyclically reproducing from said'medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first signal and a second reproduced signal corresponding to said second signal; and cyclically-operative indicating means cyclically actuated by said different reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from the cyclically moving medium.

' 4. In a system for studying transient signal occurrences and associated with a source of at least a first transient signal and second transient signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable frequency range; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each of said carrier currents being of a frequency repmducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providin thereby a corresponding first modulated signal and for modulating the second carrier ourleast a first transient signal and second transient signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable frequency range and having at least two endless recording tracks; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each rent by the second signal and providing thereby a corresponding second modulated signal of such characteristics that the different modulated signals may be combined into a composite signal out of which the diiferent modulated signals may be derived; recording means for recording on said medium said composite signal corresponding to said first modulated signal and second modulated signal; reproducing means including demodulating means and filtering means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first signal and a second reproduced signal corresponding to said second signal; and cyclically-operative indicating meanscyclically actuated by said different reproduced signals for simultaneously visually presenting image corresponding to the different signals reproduced from the cyclically moving medium.

5. In a system for studying transient signal occurrences and associated with a source of at least one transient signal and an auxiliary signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable frequency range; said auxiliary signal being reproducibly recordable on said medium; carrier frequency supply means for supplying a carrier current of a frequency reproducibly recordable on said moving recording medium modulating means for modulating the carrier current by the signal and providing thereby a corresponding modulated signal; recording means for recording on said medium signals corresponding to said transient signal and said auxiliary signal; reproducing means including demodulating means for cyclically re producing from said medium the recorded signals 6. In a system for studying transient signal 10 occurrences and associated with a source of at least one transient signal and an auxiliary signal: an endless cyclically-moving recording medium of a limited reproducibly-recordable frequency range and having at least two endless recording tracks; said auxiliary signal being reproducibly recordable on said medium; carrier frequency supply means for supplying a carrier current of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the carrier current by the transient signal and providing thereby a corresponding modulated signal; recording means for recording on the difierent tracks of said medium signals corresponding to said transient signal and said auxiliary signal; reproducing means including demodulating means for cyclically reproducingfrom said medium the recorded signals and for cyclically supplying from the reproduced signals a reproduced signal corresponding to said transient signal and an auxiliary reproduced signal corresponding to said auxiliary signal; and cyclicallyoperative indicating means cyclically actuated by said difierent reproduced signals for simultaneously visually presenting images corresponding to the difierent signals reproduced from the cyclically moving medium.

'7. In a system for studying transient signal occurrences and associated with a source of at least a first signal and second signal and an auxiliary 40 signal: an endless cyclically-moving recording medium of a limited reproducibly-recordablefrequency range; said auxiliary signal being reproducibly recordable on said medium; carrier frequency supply mean for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal recording means for recording on said medium signals corresponding to said first modulated signal and second modulated signal and said auxiliary signal; reproducing means including demodulating means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first signal and a second reproduced signal corresponding to said second signal and an auxiliary reproduced signal corresponding to said auxiliary signal; and cyclically-operative indicating means cyclically actuated by said different reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from 7 the cyclically moving medium.

8. In a system for studying transient signal occurrences and associated with a source of at least a first transient signal and second transient signal and an auxiliary signal: an endless cyclicallymoving recording medium of a limited reproducibly-recorded frequency range; said auxiliary signal being'reproducibly recordable on said medium; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency difiering from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal of such characteristics that the difierent modulated signals may be combined into a composite signal out of which the different modulated signals may be derived; recording ineans for recording on said medium said auxiliary signal and said composite signal corresponding to said first modulated signal and second modulated signal; reproducing means including demodulating means and filtering means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first transient signal and a second reproduced signal corresponding to said second transient signal and an auxiliary reproduced signal corresponding to said auxiliary signal; and cyclically-operative indicating means cyclically actuated by said different reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from the cyclically moving medium.

9. In a system for studying transient signal occurrences and associated with a source of at least a first transient signal and second transient signal and an auxiliary signal: an endless cyclicallymoving recording medium of a limited reproducibly-recordable frequency range and having at least two endless recording tracks; said auxiliary signal being reproducibly recordable on said medium; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency differing from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal of such characteristics that the different modulated signals may be combined into a composite signal out of which the different modulated signals may be derived; recording means for recording on the diiferent tracks of said medium said auxiliary signal and a composite signal corresponding to said first modulated signal and second modulated signal; reproducing means including demodulating' means and filtering means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced I sponding to the different signals reproduced from the cyclically moving medium;

10. In a system for studying transient signal occurrences and associated with a source of at least a first transient signal and second transient signal: an endless cyclically-moving magnetic recording medium of a limited reproducibly-recordable frequency range; carrier frequency supply v means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency diflering from said first frequency, each of said carrier currents being of a irequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal; recording means for recording on said medium signals corresponding to said first signal and second signal; reproducing means including demodulating means for cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a first reproduced signal corresponding to said first signal and a second reproduced signal corresponding to said second signal; and oscilloscope means cyclically actuated by said difierent reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from the cyclically moving medium,

the cyclical rate of said medium being sufiiciently high so that a substantially steady image corresponding to said diflerent reproduced signals is simultaneously presented by said oscilloscope means.

11. In a vsystem for studying transient signal occurrences and associated with a source at least a first transient signal and'second tran ent signal: an endless cyclically-moving magnetic recording medium of a limited reproducibly-recordable frequency range; carrier frequency supply means for supplying a first carrier current of a first frequency and a second carrier current of a second frequency difiering from said first frequency, each of said carrier currents being of a frequency reproducibly recordable on said moving recording medium; modulating means for modulating the first carrier current by the first signal and providing thereby a corresponding first modulated signal and for modulating the second carrier current by the second signal and providing thereby a corresponding second modulated signal of such characteristics that the different modulated signals may be combined into a composite signal out of which the different modulated signals may be derived; recording means for recording on said medium said composite signal corresponding to said first modulated signal and second modulated signal: reproducing means including demodulatlng means and filtering means for cyclically reproducing from said medium the recorded. signals and for cyclically supplying least one transient signal and an auxiliary signal:

an endless cyclically-moving magnetic recording medium or a limited reproducibly-recordable frequency range and having at least two endless recording tracks: said auxiliary signal being reproducibly recordable on said medium; carrier irequeasy supply means for supplying acarrier cur rent of a frequency reproducibly'recordable on said moving recording medium; modulating means for modulating the carrier current by the tran sient signal and providing thereby a corresponding modulated signal recording means for record, ing on the diiierent tracks of said medium signals corresponding to said transient signal and said auxiliary signal; reproducing means including demodulating means ior cyclically reproducing from said medium the recorded signals and for cyclically supplying from the reproduced signals a reproduced signal corresponding to said transient signal and an auxiliary reproduced signal correl sponding to said auxiliary signal; and oscilloscope means cyclically actuated by said diflerent reproduced signals for simultaneously visually presenting images corresponding to the different signals reproduced from the cyclically moving medl- 40 um, the cyclical rate of said medium being sumsponding to the different reproduced signals to be visually presented in different positions.

14. A system as defined by claim 11 in which the oscilloscope means include means operative in synchronism with the cyclic operation of said recording medium for causing the images corre spending to the different reproduced signals to be visually presented in diiierent positions.

15. A system as defined by claim 12 in which the oscilloscope means include means operative in synchronism with the cyclic operation of said recording medium for causing the images corresponding to the different reproduced slsnals to be visually presented in difierent positions.

' JOHN a senior, as. 

